The future of library services may lie in a mottled black-and-white square the size of a Post-it note.

The Contra Costa County library has teamed up with Tri Delta Transit to display QR codes, essentially bar codes for smart phones, on all East County buses. When scanned with a phone, these codes take users to a newly launched website featuring 600 audio books available for instant download.

Eventually, the library hopes to bring this “Snap ‘n Go” technology to spots throughout the county, including museums, cafes and hospital waiting rooms.

This is bringing library service anywhere you can stick a two-inch code,” Library Information Systems Manager Paula MacKinnon said.

People with older smart phones may need to download a free QR reader from the library’s website, and all users must download library software that transfers the books and automatically deletes them after 14 days. All of this can be done from the bus, and the mobile website provides a connection to live help by voice, text or instant messaging.

“Once they try it, this is gonna catch on quickly,” Mike Furnary of Tri Delta Transit said. “The QR codes make it very fast.”

QR, or “quick response,” codes use two-dimensional bar code technology pioneered in Japan to communicate information to wireless devices. The codes are increasingly found on product labels, catalogs and advertisements in the United State, but the Snap ‘n Go program is the first one of its kind, according to library officials.

Audio books are also gaining popularity at libraries nationwide as a free, convenient way to enjoy the latest bestseller while enduring traffic or sweating through a gym workout. Contra Costa library patrons downloaded more than 4,000 audio books in July. Patrons have long been able to download audio books to their home computers, but can now use the mobile website to download books to their smart phones no matter where they are.

The most popular were “Learn Spanish in your Car,” “Get Organized the Clear and Simple Way” and the 1950s cult classic “Atlas Shrugged. “

The new mobile website has rarely drawn more than 100 daily visitors since its launch last month, but organizers say that people are still finding out about the service. Contra Costa has the 10th longest average commute time west of the Mississippi, MacKinnon said, and is above the national average in smart phone usage.

Tri Delta Transit’s 69 buses provide 10,000 rides a day around East County, but commute times rarely exceed 45 minutes. The library is hoping to bring Snap ‘n Go posters to busses that travel longer routes, such as the WestCat bus system, which runs from Hercules to San Francisco.

MacKinnon also wants to pair library QR codes with museum exhibits and bring them into cafes, where a physical collection would be too vulnerable to theft. She envisions patients passing the time with downloaded audio books during hospital visits.

“It would open up a lot more content to them in a location where if they didn’t bring their own book, they’re stuck with People magazine from 2003,” she said.

The library has had success in the past couple of years with a program that brings automated book receptacles to BART stations. But while the large, futuristic Library-a-go-go machines are hard to miss, people may fail to recognize the new QR codes as portals to paperless books.

MacKinnon also acknowledges that smart phone users may be less likely than other commuters to seek out library content because they already have access to the Internet.

Still, MacKinnon hopes that the novelty of the technology and tedium of the commute will convince some library users to lend an ear to the new program.

“We’re not in competition with other things you can get on your phone,” she said. “We’re a complement. Just take a picture of a code and see what happens.”